Structural Organisation Of The Brainstem Flashcards
What is the brainstem made up of?
Medulla oblongata
Pons
Midbrain
If the brainstem were to be cut in transverse sections what would the four areas seen be?
(Posterior to anterior)
Tectum (roof of ventricular system)
Ventricular system
Tegmentum (core of the brainstem)
Basal portion (most anterior)
What are the three broad functions of the brainstem?
Connects the tracts to higher centres
Contains reflex centres
Houses nuclei of cranial nerves 3-12
Where is the midbrain/ mesencephalon found?
Located between the Diencephalon and the pons
Where is the cerebral aqueduct found?
The cerebral aqueduct is hollow and runs through the midbrain and connects the 3rd and 4th ventricles
Which cranial nerves emerge from the midbrain?
Oculomotor (3)
Trochlear (4)
What is the corpora quadrigemina?
It is a reflex centre that connects the midbrain to the hindbrain
How is the corpora quadrigemina divided?
2 superior colliculi
2 inferior colliculi
What reflexes are the superior colliculi responsible for?
Control reflex movements of the eyes, neck, and head in response to visual stimuli
What reflexes are the inferior colliculi responsible for?
Control reflex movements of the head, neck and trunk in response to auditory stimuli
Where is the red nucleus found?
It is a large subcortical structure in the ventral midbrain
How is the red nucleus divided?
The red nucleus is cytoarchitectonically divided into two histologically distinct subregions
What are the two regions of the red nucleus?
A magnocellular caudal region - large sparse neurones
Rostral parvocellular region - small and medium neurones
What’s the role of the red nucleus?
It is a relay station
And integrates information
Issues subconscious motor commands concerned with muscle tone and posture
Where does the red nucleus receive information from?
It contains various blood vessels and will receive information from the cerebrum and cerebellum
Where is the substantia nigra?
It is found lateral to the red nucleus
What does the substantia nigra do?
The melanin containing substantia nigra secretes dopamine to inhibit the excitatory neurones of the basal nuclei
What is the difference between a healthy individuals and someone with Parkinson’s brain scan?
The Parkinson’s patient will lack dark spots (Dopaminergic neurones) as there is damage to the substantia nigra
Where is the pons found?
The pons is found between the midbrain and medulla oblongata
Acts as a bridge?
What are the two surfaces of the pons?
Anterior surface - large bulge (basilar pons)
Posterior surface - cerebellar peduncles (tegmentum)
Where is the locus coeruleus found?
It is located within the dorsal wall of the upper pons, under the cerebellum in the caudal midbrain
It is also surrounded by the 4th ventricle
What is the importance of the locus coeruleus?
This nucleus is one of the main sources of noradrenaline in the brain
It is composed of mostly medium sized neurones
What is different about the locus coeruleus?
Melanin granules inside it contribute to it being coloured blue
Which cranial nerves emerge from the groove between the medulla and pons?
6, 7, 8
Which nuclei are associated with the pons?
Sensory and motor nuclei of cranial nerves 5, 6, 7, 8
What are the two respiratory centres found in the pons?
Apneustic centre
Pneumotaxic centre
What is apneusis?
A disturbance of respiratory rhythm characterised by sustained gasping inhalation
Increased Inspiratory effort
What does the apneustic centre do?
It is thought to excite the inspiratory centre by gradually increasing the firing rate of inspiratory muscles
What does the pneumotaxic centre do?
Prevents apneusis by promoting coordinated respiration
Describe a little about the medulla oblongata
It connects to the pons superiorly
Connects to the spinal cord inferiorly
Contains long ascending and descending tracts to higher centres
Allows brain and spinal cord to interact
Coordinates complex autonomic reflexes
Controls visceral functions
What are the components of the anterior surface of the medulla oblongata?
Pyramids - contain corticospinal tracts
Decussation of pyramids
Olives - underlying olivary nuclei
What are the two tubercles of the posterior aspect of the medulla oblongata?
Gracile tubercle
Cuneate tubercle
What is the reticular formation?
A set of interconnected nuclei that are located in the brainstem, hypothalamus and other regions
What does the reticular formation do?
Reticular activating system for alertness
Filter out repetitive or familiar stimuli it is inhibited by sleep, alcohol and drugs
What are the distinct levels of the vertebral column?
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
What is important to remember about the cervical spine?
There are 7 cervical vertebrae but 8 cervical nerves!
The first 7 exist superiorly to their vertebra while the 8th exists caudally
How many vertebrae does each distinction have?
Cervical - 7
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccyx - fused
How many spinal nerves are there?
31 pairs
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Where does the spinal cord end?
In adults around L1/2
In children closer to L3
What is the name of the end point of the spinal cord?
The conus medullaris
What projects from the conus medullaris?
The cauda equina (horses tail)
This will contain the remaining spinal nerves that project to their corresponding vertebrae
What are the denticulate ligaments?
They anchor the chord within the dural sac
What is the filum terminale?
It is a fibrous band that extends from the conus medullaris to the periosteum of the coccyx
What is the function of the filum terminale?
To fixate, stabilise and buffer the distal spinal cord from normal and abnormal cephalic and caudal traction
What is the lumbar cistern?
The subarachnoid space in the lower lumbar spinal canal
It is an enlargement of the subarachnoid space in the dural sac distal to the conus medullaris
Where in the spinal cord is it suitable to take a lumbar puncture?
In adults between L3-L4
In children between L4-L5
What is the organisations of white and gray matter in the body?
Spinal cord - grey inside, white outside
Brain - white inside, grey outside
How does the spinal cord look in cross section?
Butterfly shape of grey matter
The grey matter is capped with substantia gelatinosa
Surrounded by white matter
What is a funiculus?
A bundle containing one or more tracts/ fasiculi
What connects the two halves of the spinal cord?
They are connected by a gray commissure
What are the three funiculi of the spinal cord?
Dorsal (posterior)
Lateral
Anterior (ventral)
Where is the dorsal funiculus found?
Between the dorsal horn and the dorsal-median septum
Where is the lateral faniculus found?
Between where the dorsal root enter and the ventral roots exit the spinal cord
Where is the anterior faniculus found?
Between the anterior median fissure and the site where anterior roots exit
What is the organisation of motor vs sensory fibres in the spinal cord
Motor function fibres are found more dorsally while sensory functions are found more centrally
